The Hollywood Reporter says the third installment was in preproduction and set for a spring shoot for a planned May 2010 release. The development puts the participation of the talent attached in doubt, adds the trade. Michael Apted was on board to direct a script by Steven Knight. The key players of the second installment, “Prince Caspian” — Ben Barnes, Georgie Henley, William Moseley and Anna Popplewell — were to return for the third film.

Walden has a strong relationship with the C.S. Lewis estate and will shop “Treader” in hopes of finding a new partner. The most likely candidate at this stage is Fox, which markets and distributes Walden fare under the Fox Walden banner.

Any partnership on a “Narnia” movie will require a substantial investment, however. “Caspian,” which filmed in the Czech Republic, Mexico and New Zealand, cost $200 million. The first film, “The Lion, the Witch and the Wardrobe,” was shot mostly in New Zealand for $180 million.